I got this message in tty1 after I installed obarun and rebooted into it: 
fsck reports errors -- at least system should be rebooted
After fsck them using liveiso and reboot again this message is still here.

The complete messages in tty1 are: 
:: running early hook [udev]
:: running hook [udev]
:: Triggring uevents...
:: performing fsck on '/dev/sda5'
:: ROOT: clean, ???/??? files, ???/??? blocks
:: mounting '/dev/sda5' on real root
:: running cleanup hook [udev]

[Starts stage1 process...]
66-boot: info: Create live scandir at: /run/66
66-boot: info: Initiate earlier service of tree: boot
66-boot: info: Starts boot logger at: /run/66/log/0
fsck reports errors -- at least system should be rebooted


   Welcome to Obarun Linux
And the log are: 
$ cut -c 27- /run/66/log/0/current | grep -A6 system-fsck
[system-fsck] starts...
/dev/sda5 is mounted.
e2fsck: Cannot continue, aborting.


fsck reports errors -- at least system should be rebooted
[mount-fstab] starts...
I followed this guide https://wiki.obarun.org/doku.php?id=uefi to install it and used the following command to create a boot entry: 
$ sudo efibootmgr                   \
  --create --verbose --label Obarun \
  --disk /dev/sda --part 3          \
  --loader /vmlinuz-linux           \
  --unicode                         \
  'root=LABEL=ROOT rw initrd=/intel-ucode.img initrd=/initramfs-linux.img'
I also checked the initrd: 
$ zcat /boot/initramfs-linux.img | cpio -id
$ cat -n hooks/udev
     1	# !/usr/bin/ash
     2	
     3	run_earlyhook() {
     4	    udevd --daemon --resolve-names=never
     5	    udevd_running=1
     6	}
     7	
     8	run_hook() {
     9	    msg ":: Triggering uevents..."
    10	    udevadm trigger --action=add --type=subsystems
    11	    udevadm trigger --action=add --type=devices
    12	    udevadm settle
    13	}
    14	
    15	run_cleanuphook() {
    16	    udevadm control --exit
    17	    udevadm info --cleanup-db
    18	}
    19	
    20	# vim: set ft=sh ts=4 sw=4 et:
It seems like fsck in boot-66serv/service/boot/system/system-fsck will fail unconditionally because ROOT partition have already be fscked and then mounted by udev.
So this error report is a false one and can be ignored, isn't it?


update:
--disk /dev/sda --part 5
--disk /dev/sda --part 3
Is /dev/sda5 really your root? I have had that manual-situation I never thought were really a thing in reality where my disks got swapped (sda <-> sdb)
Might also wanna double check your fstab and make sure you're using UUIDs or something other than sdX.
fungalnet wrotewhat file system did you use for root?
It's ext4.
marianarlt wroteIs /dev/sda5 really your root? I have had that manual-situation I never thought were really a thing in reality where my disks got swapped (sda <-> sdb)
Might also wanna double check your fstab and make sure you're using UUIDs or something other than sdX.
Yes, /dev/sda5 (labeled "ROOT") is root:
$ lsblk -o NAME,LABEL,FSTYPE,MOUNTPOINT,UUID,PARTUUID
NAME   LABEL FSTYPE MOUNTPOINT UUID                                 PARTUUID
sda                                                                 
├─sda1                                                              291a8028-87db-423f-9404-72c001e2d668
├─sda2 DATA  ntfs              681651521651227C                     af955944-240b-47f8-ba09-e3c871592525
├─sda3 ESP   vfat   /boot      8CAA-122F                            2acb1002-37da-427d-bbae-b810e3ab2a9e
└─sda5 ROOT  ext4   /          a8b1b304-02e9-4903-b6d1-ec69c97fc62b a5c5d778-e0ff-460f-a7ed-a40ac5fe9009
efibootmgr says: 
$ efibootmgr -v
BootCurrent: 0000
Timeout: 0 seconds
BootOrder: 0000,0001,2003,2001,2002
Boot0000* Obarun	HD(3,GPT,2acb1002-37da-427d-bbae-b810e3ab2a9e,0x5b706800,0x200000)/File(\vmlinuz-linux)r.o.o.t.=.L.A.B.E.L.=.R.O.O.T. .r.w. .i.n.i.t.r.d.=./.i.n.t.e.l.-.u.c.o.d.e...i.m.g. .i.n.i.t.r.d.=./.i.n.i.t.r.a.m.f.s.-.l.i.n.u.x...i.m.g.
Boot0001* Windows Boot Manager	HD(1,GPT,4dab3c62-1684-4919-90d0-2bb6c504f4d7,0x800,0x82000)/File(\EFI\Microsoft\Boot\bootmgfw.efi)WINDOWS.........x...B.C.D.O.B.J.E.C.T.=.{.9.d.e.a.8.6.2.c.-.5.c.d.d.-.4.e.7.0.-.a.c.c.1.-.f.3.2.b.3.4.4.d.4.7.9.5.}...O................
Boot0004* EFI Network 0 for IPv4 (54-E1-AD-09-F8-72) 	PciRoot(0x0)/Pci(0x1c,0x3)/Pci(0x0,0x0)/MAC(54e1ad09f872,0)/IPv4(0.0.0.00.0.0.0,0,0)RC
Boot0005* EFI Network 0 for IPv6 (54-E1-AD-09-F8-72) 	PciRoot(0x0)/Pci(0x1c,0x3)/Pci(0x0,0x0)/MAC(54e1ad09f872,0)/IPv6([::]:<->[::]:,0,0)RC
Boot0006* EFI Network 0 for IPv4 (54-E1-AD-09-F8-72) 	PciRoot(0x0)/Pci(0x1c,0x3)/Pci(0x0,0x0)/MAC(54e1ad09f872,0)/IPv4(0.0.0.00.0.0.0,0,0)RC
Boot0007* EFI Network 0 for IPv6 (54-E1-AD-09-F8-72) 	PciRoot(0x0)/Pci(0x1c,0x3)/Pci(0x0,0x0)/MAC(54e1ad09f872,0)/IPv6([::]:<->[::]:,0,0)RC
Boot2001* EFI USB Device	RC
Boot2002* EFI DVD/CDROM	RC
Boot2003* EFI Network	RC
The output of PARTUUID(2acb1002-37da-427d-bbae-b810e3ab2a9e) in running system match efi entry and this entry use "root=LABEL=ROOT" to find root partition. It's really hard to type uuid in "sudo efibootmgr --create --unicode='root=UUID=???'" when create it. So I followed your recommendation(i.e. use label) here.

fstab use /dev/sda5 instead of UUID: 
$ cat -n     /etc/fstab
     1	# UUID=a8b1b304-02e9-4903-b6d1-ec69c97fc62b LABEL=ROOT
     2	/dev/sda5           	/         	ext4      	rw,relatime	0 1
     3	
     4	# UUID=8CAA-122F LABEL=ESP
     5	/dev/sda3           	/boot     	vfat      	rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro	0 2
     6
This is obarun-install's default. I forgot to use "genfstab -U".
I did some experiment.

Backup /etc/fstab: 
$ sudo cp /etc/fstab{,~}
Use "genfstab -U" but skip root: 
 
$ genfstab -U -f /boot / | sudo tee /etc/fstab | cat -n
     1	# /dev/sda3 LABEL=ESP
     2	UUID=8CAA-122F      	/boot     	vfat      	rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro	0 2
     3
root is mounted after reboot and the error report in the boot process disappears: 
$ sudo reboot

$ lsblk -o NAME,LABEL,FSTYPE,MOUNTPOINT
NAME   LABEL FSTYPE MOUNTPOINT
sda                 
|-sda1              
|-sda2 DATA  ntfs   
|-sda3 ESP   vfat   /boot
`-sda5 ROOT  ext4   /
That's of help, thank you for the solution. Did you confirm that fsck checks root still (I suppose so)?
Yes, the messages in tty1 are the same as before except the error reports.
:: running early hook [udev]
:: running hook [udev]
:: Triggring uevents...
:: performing fsck on '/dev/sda5'
:: ROOT: clean, ???/??? files, ???/??? blocks
:: mounting '/dev/sda5' on real root
:: running cleanup hook [udev]

[Starts stage1 process...]
66-boot: info: Create live scandir at: /run/66
66-boot: info: Initiate earlier service of tree: boot
66-boot: info: Starts boot logger at: /run/66/log/0
fsck reports errors -- at least system should be rebooted


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